Patent Application
20120132416
The invention relates to recovering natural resources such as oil and natural gas from a geological formation; particularly the invention related to a method, apparatus and system for stimulating wells using acoustic waves during a treatment of the well by one or more existing applications for stimulating wells.
There exist several extraction methods to improve productivity from oil wells. However in the upstream crude oil industry, 60% to 70% of Original Oil In Place (OOIP) is typically left in the reservoir after the use of normal primary and secondary recovery techniques (Society of Petroleum Engineers. www.spe.org). The benefits of improving extraction methods are substantial. For example, there are thousands of oil wells in Texas, USA, alone, which could benefit from improving oil production output. If it were possible to recover even 50% of the heavy oil deposits, the US could supply 50% of North American demand for another 50 to 75 years (Dr. Franklin Foster, 2006).
A well for extracting fluids from geological formations is constructed by drilling a hole from the surface toward the geological formation that contains a natural resource, and that has adequate permeability to let fluids produced in the formation flow toward the well. The well's walls are lined with a cement layer and a casing that houses and supports a production tube string coaxially installed in its interior. In addition, perforations are made in the well lining in order to connect the well with the reservoir, supplying a path or trajectory inside the formation. Tubes provide an outlet for the fluids obtained from the formation.
Typically, there are numerous perforations that extend radially from the lined or coated well. Perforations are uniformly separated in the lining, and pass to the outside of the lining through the formation. In an ideal case, perforations are only located within the formation, and their number depends on the formation thickness. It is rather common to have nine, and up to twelve perforations per depth meter of formation. Other perforations extend longitudinally, and yet other perforations may extend radially from a 0°-azimuth, while additional perforations, located every 90° may define four sets of perforations around azimuth. Formation fluids pass through these perforations and come into the lined (or coated) well.
Preferably, the oil well is plugged by a sealing mechanism, such as a shutter element, or with a bridge-type plug, located below the level of perforations. This shutter element is connected to a production tube, and defines a compartment. The production fluid, coming from the formation or reservoir, enters the compartment and fills the compartment until it reaches a fluid level. Accumulated oil, for example, flows from the formation and can be accompanied by variable quantities of natural gas. Hence, the lined compartment may contain oil, some water, natural gas, and solid particles, with normally, particles settling at the bottom of the compartment.
The fluid produced in the formation may change its phase when there is a reduction of pressure around the well; this change of phase causes the gasification of the lightest molecules. Also, the oil well can produce very heavy molecules. Over time, due to several reasons, oil well productivity gradually diminishes. Two main causes of the reduction in productivity are related to relative permeability: a decrease of the fluidity of crude oil, and the deposit of solids in the perforations.
Crude oil's fluidity diminishes over time and progressively obstructs pores in a deposit or reservoir. On the other hand, solids such as clays, colloids, salts, paraffin etc. accumulate in perforation zones of the well. These solids reduce the absolute permeability, or interconnection between pores. Problems associated with the causes mentioned above are: obstruction of pores by mineral particles that flow jointly with the fluid to be extracted, precipitation of inorganic scales, decanting of paraffins and asphalt or bitumen, hydration of clay, invasion of solids from the mud and filtration of perforation mud, as well as invasion of termination fluids and solids from brine injections. Each of the above mentioned causes can produce a permeability reduction, or a flow restriction in the zone surrounding oil well perforations. This defines the pore size connecting to the fluid inside formation, allowing the fluid flow from the formation through cracks or fissures, or connected pores, and finally the fluid comes to interstitial spaces within the compartment and is collected. During that flow, very small solid particles from the formation, called “fines,” may flow; but instead they tend to settle.
After a certain time, trajectories through perforations extending inside the formation of a reservoir may become obstructed with “fines” or residues. While the “fines” can be kept in a disperse state for some time, they can agglomerate and plug the pore space, reducing the fluid rate or production quantity. This may become a problem that is fed back to the well and cause a production decrease. More and more “fines” can keep settling on perforations, plugging them more and more, even tending to halt a minimum flow rate.
There exist several treatment methods to improve productivity from oil wells. Periodic stimulation of oil and gas wells is done by applying three general types of treatment: acid treatment, fracturing, and default treatment with solvents and heat. Acid treatment consists of using mixtures of acids HCl and HF (hydrochloric acid and hydrofluoric acid), which is injected in the production zone (rock). Acid is used for dissolving reactive components (carbonates, clay minerals, and in a smaller quantity, silicates) in the rock, thus increasing permeability. Frequently, additives are incorporated, such as reaction retarding agents and solvents, to improve acid performance in the acidizing operation and/or protect the equipment from acid attacks.
While acid treatment is a common treatment to stimulate oil and gas wells, this treatment has multiple drawbacks among which that the penetration depth of active (or live) acid is generally less than 5 inches (12.7 cm) into the rock. Furthermore, the cost of acids and the cost of disposing of production wastes are high. Acids are often incompatible with the crude oil; and acid may produce viscous oily residues inside the well. Precipitates may also form once the acid is consumed.
Hydraulic fracturing is another technique usually used for stimulating oil and gas wells. In this process, high hydraulic pressures are used to produce vertical fractures in the formation. Fractures can be filled with polymer plugs, or treated with acid (in rocks, carbonates, and soft rocks), to form permeability channels inside the wellbore region; these channels allow oil and gas to flow. However, the cost of hydraulic fracturing is extremely high (as much as 5 to 10 times higher than acid treatment costs). In some cases, fracture may extend inside areas where water is present. The latter may lead to an increase of the quantity of water in the extracted oil, which significantly diminish the productivity of oil.
Hydraulic fracture treatments extend several feet from the well, and are used more frequently when rocks are of low permeability. The possibility of forming successful polymer plugs in all fractures is usually limited, and problems such as plugging of fractures and grinding of the plug may severely deteriorate productivity of hydraulic fractures.
Another method for improving oil production in wells involves injecting steam. One of the most common problems in depleted oil wells is precipitation of paraffin and asphaltenes or bitumen inside and around the well. Steam has been injected in such wells to melt and dissolve paraffin into the oil or petroleum, and then all the mixture flows to the surface. Frequently, organic solvents are used (such as xylene) to remove asphaltenes or bitumen whose melting point is high, and which are insoluble in alkanes. Steam and solvents are very costly (solvents more so than steam), particularly when marginal wells are treated, producing less than 10 oil barrels per day (1 bbl=159 liters). Furthermore, in the absence of mechanical mixing, which is required for dissolving or maintaining paraffin, asphaltenes or bitumen in suspension, the application of steam and solvents is less efficient than may be expected.
Therefore, the a need for a method, apparatus and system for improving well productivity that enhance the potency of the existing enhanced oil recovery applications, and potentially reduce the cost and/or time of application of the existing technologies. The invention provides a system, apparatus and method for use in combination with enhanced oil recovery applications to increase production capacity of oil, gas and water wells.
The invention provides a system, an apparatus and methods for increasing productivity of a natural resource producing-well. The invention provides an apparatus that utilizes one or more elastic-waves generators hosted inside a chamber. The chamber is made of (or protected by) a corrosion-resistant material, that allow the apparatus to be efficiently used in harsh chemical environments.
The invention provide a highly efficient and versatile means to increase the mobility of fluids within the well bore region of an oil/water/gas-well. The method and system may be adapted to the geology of the reservoir. In one embodiment of the invention, the system utilizes an acoustic device of the “downhole” type, that is, at the bottom of the well and/or the perforated zone of the well, to generate mechanical waves of an extremely high energy. Such high energy is capable of removing deposits of fines, organics, scales and inorganic deposits inside the well and in the wellbore region. A device implementing the invention may have an insulated and controlled-environment chamber, for protection against mechanical waves generated by the acoustic generators, and against corrosion by hydrocarbons present in the formation, and from high temperature. The later configuration allows for the installation of several types of sensors and devices to acquire data from the well bottom, wellbore and/or the perforated zone.
One or more embodiments of the invention deliver an acoustic device for oil, gas, and water well, which does not require injection of chemicals for their stimulation.
The invention provides an acoustical device for stimulating wells in the perforation zone (downhole) that can operate inside a tube without needing the withdrawal or elimination said tube. Alternatively, the device may be coupled to the tube using an adapter, in order to operate while being during production.
The regime of operation in accordance with the invention may be adapted to the type of well (e.g., Oil, Gas or any combination of both), to type geology and all other aspects of factors that limit the production in a well. The method and system embodying the invention are highly versatile and may be adapted for use specifically to treat any of a plurality of conditions. Embodiments of the invention may comprise an acoustic device capable of being used in one or more different types of reservoirs, crude type, gas content, and combined environments. The acoustic device may operate with an corrosion-resistant heatsink chamber that emits and/or radiates power as elastic waves directed to the formation, and that likewise avoids the contact of hydrocarbons and other fluids with the radiator and other inner components of the system preventing corrosive damage.
Another embodiment of the invention provides a corrosion-resistant heatsink chamber that acts as an acoustic resonance chamber. The invention takes into account the disposition of the wave generator and provides a plurality of geometries that are adequate to address a plurality of conditions. The corrosion-resistant heatsink chamber also prevents the system from overheating, by means of a heatsink liquid which fills the device, allowing the system to work in gas reservoirs or oil wells with high concentration of gas. When working in heavy oil wells, the capacity to efficiently transfer the heat generated by the wave radiators to the environment, also improves the capacity of the system to reduce the viscosity of the crude oil, for example, thus facilitating the crude oil flow and extraction.
Furthermore, an embodiment of the invention provides a device that allows the connection of one or more acoustic devices in a single well, thus allowing an installation that fulfills the specific requirements for each well.
The invention provides a device for generating elastic waves that are applied to a geologic formation simultaneously with the applications of one or more enhanced oil recovery (EOR) treatment methods. The invention provides numerous alternatives to applying EOR methods alone, because the outcome of almost every existing EOR technique may be improved when used in combination with the acoustic wave application. The application of high-frequency elastic waves, low-frequency elastic waves or a combination thereof may stimulate the formation while applying an existing EOR method, which results in an increase of the efficiency of the treatment.
For example, while treating a formation with acid, the high-frequency vibration may increase the efficacy of the acid to dissolve sediments (e.g., carbonate scales and the like), while the low-frequency vibrations may open the cracks in the formation, thus allowing the acidic solution to travel deeper into the rock, react with and dissolve the debris that clog the orifices and allow the opening of more pores (deeper) into the rock. Similar applications may be contemplated using the combination of the apparatus, method and system of the invention with one or more existing EOR techniques, such as fracturing, heat and solvent treatments, and any other available treatment method.
In the extreme case of “depleted” oil wells, the combination disclosed by the invention of applying elastic waves while treating a well with an existing EOR technique, may result in the reactivation of the well. A well may be categorized as “depleted” based on the cost effectiveness of production from the well, rather than the amount of resource still present in the formation. The formation may still contains oil reserves, for example, when the flow to a specific well decreases to a point where the amount of oil recovered from that well does not justify the cost of production. In the latter case the well is considered “depleted”, and may be eventually abandoned. When a depleted well is treated in accordance with an embodiment of the invention, i.e., using a combination of elastic wave application with an existing EOR technology, the well may be reactivated and sufficient amounts of oil may become available for recovery to justify restarting production.
Elastic waves application may be combined, in accordance with embodiments of the invention, with steam/water injection. The elastic waves may be applied as high-frequency, low frequency or a combination of high- and low-frequency elastic waves while steam/water is being applied according to existing methods of treating wells with steam/water. The combination, as thought by the invention, increases the mobility of injected fluids, increase the mobility of reservoir fluids leading to an increase of productivity. The application of elastic waves in combination with the application of steam/water treatment, in accordance with the invention, allows for cleaning of the injection pores/channels, and an increase of the limit of the flow of water.
The invention teaches a method and system for combining the application of elastic waves along with chemical treatment of the well. The application of elastic waves to a well allows for deeper chemical penetration into the formation, an increased reactivity of the chemical compounds with the substrates (e.g., rocks material, sediment deposits, mineralization byproducts), increased mobility of the chemical solutions through the formation, and an alteration of the oil-to-water interface.
The invention teaches combining elastic waves application in combination with hydraulic fracturing treatments. The pressure waves created by the application of elastic waves may travel to varying distances from the well, depending on the frequency of the elastic wave. The effects of applying elastic waves to a well in combination with fracturing treatments, in accordance with embodiments of the invention, lead to a long-lasting treatment effect, an increase of oil mobility through new fractures, increased mobility of proppant particles through cracks in order to keep openings wider and, hence, lasting long for fluid flow.
Moreover, a system embodying the invention provides a plurality of sensors, data collection, data transmission and data processing modules, that may all be used during a treatment according to any EOR technique when combined with the deployment the elastic waves generating device provided by the invention. The benefits of the latter modules include optimization of the time required to treat each specific well and the adjustment of the treatment parameters in real-time (e.g., the acid solution composition in the case of the acidizing EOR, or the pressure of water in the case of hydraulic fracturing or any other parameters associated with the any other EOR).
The invention provides an apparatus, method and system for increasing production capacity of oil, gas and water wells utilizing a versatile device that is adaptable to various applications. The invention also provides methods and a system to use the device in various exploitation reservoirs that have various geologies.
In the following description, numerous specific details are set forth to provide a more thorough description of the invention. It will be apparent, however, to one skilled in the pertinent art, that the invention may be practiced without these specific details. In other instances, well known features have not been described in detail so as not to obscure the invention. The claims following this description are what define the metes and bounds of the invention.
Terminology
The following detailed description is frequently concerned with oil wells; the invention however is intended to be adapted for other types of wells to extracting other types of natural resources such as natural gas and water from geological formations.
In the following description, a reference to an enhanced oil recovery (EOR) treatment encompasses any available technology that may be used to stimulate production in a newly built well and/or a well for which stimulation is sought to increase production. A few example implementations are described in details in the following disclosure. However, one with ordinary skills in the art of oil well stimulation would recognize that numerous variations of the invention may be practiced without departing from the scope and the spirit of the invention.
In the following, a reference to a user may refers to a person, a machine (e.g., a computer) acting on behalf of a person, and in other instances a person may refer to a group of persons or a company.
Description of the General Concept
In embodiments of the invention, the wave radiator may deliver acoustic waves, mechanical waves, electromagnetic waves or any type of physical phenomenon capable of delivering vibrational energy to a geological formation.
The system embodying the invention comprises a sub-system 130 for collecting data 136 from the operating area, including the geological formation. The data collection/monitoring system 130 comprises one or more sensors for collecting a plurality of environmental data. For example, the sensors may collect temperature, pressure, viscosity, conductivity or any other physical parameter that may indicate one or more characteristics of a well. The data once collected may be transmitted, through data transmission means (e.g., copper cables, fiber optics or any other available data transmission means) 132 to a processing and control system 110.
The data processing and control system comprises one or more data processing devices, including digital computers, data visualization machines and power control units. The data processing and control system also allows a user to monitor operations and provide manual input for adjustment. The data processing and control system may execute one or more computer programs for analyzing data and one or more computer programs to provide optimization solutions to maximize the system's efficiency.
The output 122 of the data processing and control system 110 may be utilized to drive the wave radiator 120, by providing for example, instructions to the wave radiator 120, which instructions will be used by the wave radiator 120 to vary the power output to the geological formation 150 in order to achieve the best results in terms of productivity. The data processing and control unit 110 may on the other hand control the power directly fed into the wave radiator 120 in order to control the amount of power delivered to the reservoir.
The data processing and control system 110 may also feed data back to the sensing and monitoring system (e.g., 134) in order to better control the data collection process.
The invention provides using a system as described above for radiating a well and the formation in combination with one or more applications of existing enhanced oil recovery (EOR) treatments. Application of elastic waves to the well bottom and/or formation provides a synergistic effect, whereby the effects of a treatment using one or more existing EOR treatments is enhanced by the pressure waves provided by the system of the invention.
Existing EOR treatments typically rely on the injection of fluids (e.g., 162) into the well. The consistency of the fluids and the amount of pressure under which the fluid is applied are selected according to the type of results to be achieved. For example, hydraulic fracturing treatment (also known in the art of oil recovery as fracking) relies on the injection of water at a high pressure in order to create new fissures in the rock formation and/or augment existing ones. The high pressure mechanically causes fissures to appear in the rock formation. In addition, the water is loaded with solid particles (e.g., sand grains, pebbles etc., also known in the art of oil recovery as proppants) that penetrate the fissures and cause the cracks to remain open once the pressure from the water is removed.
Other EOR treatments rely on loading the fluids with a mixture of acid and/or chemicals. The goal of such substances is many folds: acid may dissolve mineral deposits, organic compounds may dissolve oil and/or oily residues, surfactant may be used to protect equipment from the caustic environment in the presence of chemicals and/or acids.
Block 162 represents the application of one or more fluids In order to open new passage ways (e.g., new cracks) or clear existing ones. Existing EOR treatments rely on high pressure to push a fluid, such as water into, the formation. The fluids may also contain gas (e.g., CO2, H2S, air or any other available gas in any combination of concentration in a mixture), and/or a liquid and/or steam.
Each existing EOR treatment requires a specific system for application. Since the amount of pressure used, the fluid and the consistency of the fluid can be significantly different, a system (e.g., 160) comprises pumping systems, monitoring systems, fluid supply, fluid storage and spent fluid recovery system. In the industry of oil and/or gas recovery, entire companies may become specialized in only one or a few EOR treatments, given the complexity of each one of the treatments and the various logistics involved in each application.
Block 166 represents the fluid supply to the EOR treatment system. Typically, a fluid may be prepared on-site (or transported from a remote location), and is provided to the application system (e.g., 160). Treatment typically involves equipment for recovering (and disposing of) spend fluid (e.g., block 168).
EOR treatments reactivate the flowing of the natural resource after a blockage by sediment deposit, decantation, mineralization, paraffin and/or any other substance that may contribute to clogging the passage ways. Each one of the physical phenomena involved in improving well productivity can be aided by the application of elastic waves. High frequency elastic waves cause materials to shake at a very small scale, thus providing a mixing effect which augments the reactivity of chemicals and/acids with their substrates. Low-frequency vibrations cause fissures to open wider under the effect of pressure waves and allow the proppants to penetrate deeper into the fissures, thus causing the passage ways to open wider, and letting more natural resource fluids flow through more easily.
Deployment Environment and Context of Operations
Typically, there are numerous perforations (e.g., 240) that extend radially from the lined or coated well. Perforations are generally uniformly separated in the lining, and pass to the outside of the lining through the formation. In an ideal case, perforations are only located within the formation, and their number depends on the formation thickness. It is rather common to have nine (9), and up to twelve (12) perforations per depth meter of formation. Other perforations extend longitudinally, and yet other perforations may extend radially from a 0°-azimuth, while additional perforations, located every 90° may define four sets of perforations around azimuth. Formation fluids pass through these perforations and pass into the lined (or coated) well.
Preferably, the oil well is plugged by a sealing mechanism, such as a shutter element (e.g., 232), and/or with a bridge-type plug, located below the level of perforations (e.g., 234). The shutter element 232 may be connected to a production tube, and defines a compartment 205. The production fluid, coming from the formation or reservoir, enters the compartment and fills the compartment until it reaches a fluid level. Accumulated oil, for example, flows from the formation and can be accompanied by variable quantities of natural gas. Hence, the lined compartment 205 may contain oil, some water, natural gas, and solid residues, with normally, sand settling at the bottom of the compartment.
A tool 100 for stimulating the well in accordance with embodiments of the invention, may be lowered into the well to reach the level of the formation. The tool may be connected to the ground surface through an attachment means 250 or simply attached to the extremity of the tube 230 using an adapter (see below), or even between two portions of the tube 230 (e.g. when the well has more than one extraction zone, more than one tool may be lowered). Thus, a tool 100 may be lowered momentarily into a well for well treatment, or alternatively by attaching the tool between two portions of the tube 230 or to the end of the tube 230, the tool may be operated even as the production continues from the well. The attachment means comprises a set of cables for providing the mechanical strength for holding the weight of tool 100. The attachment means may also comprise power cables for transmitting electrical energy to the tool, and communication cables such as copper wires and/or fiber optics for providing a means of transmitting data between control computers on the ground and the tool.
Area 260 represents a magnification of a small area of the rock formation, showing the details of cracks (e.g., 262) in the formation and how scaling (e.g., 264) due, for example, to mineral depositing leads to the narrowing of an opening 266. Over time, the layer 264 of deposits grows, thus narrowing the fissures and closing the passage ways though which natural fluids flow. In the latter case, acidizing treatment is adequate to dissolve the mineral deposits and increase the diameter of the orifices.
Area 270 represents a magnification of small area showing the details of cracks (e.g., 272) in a rock formation where hydraulic fracturing treatment is schematically represented. Cracks in the formation are flared under the pressure of water from the EOR treatment. The proppants 274 travel through the cracks under pressure and settle therein, thus preventing the cracks from closing after the pressure has been removed.
The invention provides a method and system for applying low-frequency and high-frequency elastic waves in combination with the application of one or more EOR treatments. For example, the high-frequency 280 elastic waves provide the capability of energetically mixing the chemicals/acids with the materials of the rock and/or the sediments blocking the pores. The application of such high-frequency vibrations has a synergistic effect promoting the effects of the application of any treatment that involves a reaction (chemical or otherwise) at the microscopic level.
Low-frequency elastic waves 285 have a wave length in the macroscopic range, and are capable of displacing solids as well as fluids. Furthermore, because of their large wave-length, low frequency elastic waves are able to travel over a long distance. Due to the latter properties, application of low-frequency elastic waves, in accordance with the invention, may promote a more efficient settling of proppant in the fissures than would have otherwise be expected with hydraulic fracturing treatment alone, for example.
General Description of an Elastic Waves Generating Device
Chamber 320 provides an important role for implementing embodiments of the invention. Chamber 320 provides an environment in which temperature, pressure and other physical parameters may be controlled in order to provide an adequate environment for an efficient functioning of device 100. For example, chamber 320 may be filled with a liquid that acts as a heat sink in order to protect equipment from the heat generated during operation. Chamber 320 may be designed with specific resonance properties to optimize the efficiency of the vibrations. Chamber 320 may be sealed to allow for high pressure inside the chamber in order to counteract the cavitation phenomena that may accompany application of sound waves to the liquid filling the chamber.
Device 100 comprises a power supply unit 330. The power supply unit comprises electronic circuitry, such as one or more circuit boards for converting power (Alternating and/or direct power) into one or more regimes of power as required by any specific type of wave radiation means comprised in the device 100. Power supply unit 330 also comprises energy storing components (e.g., one or more capacitors) capable of storing electric power and delivering the power, either automatically and/or under the control of an electronic signal.
Device 100 comprises a sensing system 340 which includes one or more sensors capable of detecting physical parameters in the well and collecting data that can be transmitted to and processed by data processing centers. The sensors may be hosted within a chamber that may be part of other chambers of device 100. Alternatively, the sensors may be hosted in a chamber that is connected with other chambers through an opening 250. The latter may be useful for allowing the liquid acting as a heat sink to freely flow and protect the sensors.
Device 100 may be constructed partly or in its entirely from corrosion-resistant materials. In accordance with embodiments of the invention, device 100 is designed to resist the harsh chemical environment attacks present in the operation zone. For example, device 100 may be constructed using a steel cylinder having a wall thickness adequate for heat dissipation and vibration transmission adequate for desired sound and temperature properties for a specific application environment, while the surfaces are coated with a corrosion-resistant compound in order to protect the device and its components from chemical attacks.
Details of an Elastic-Wave Generating Device
The chamber 460 may be made of a corrosion-resistant material, elastic enough for resisting mechanical vibrations. Chamber 460 comprises two (2) sections: a protective chamber 462 and a controlled-environment chamber 464. The protective chamber 462 comprises an upper cover 420, a separator 450, and a chamber wall 440. The controlled-environment chamber 464 houses measurement and control sensors 435, and is resistant to mechanical waves produced by the wave radiator.
Device 400 comprises a wave radiator 430. The wave radiator may have any form, and may be fabricated using materials that conducive to producing vibration waves such one or more magnetostrictive transducers. The invention allows for implementing transducer of several types and shapes depending of the target application, which in turn depends on the conditions in each formation.
In the example of
The upper cover 420 and the separator 450 may be made of corrosion-resistant materials, and are specially designed to support the high pressure present in perforated zone of the well 210. The controlled deformation chamber is flooded with an insulator heat-sink liquid 445. This heat-sink liquid 445 surrounds the wave radiator 430. Said liquid 445 has a cooling function, allowing dissipation of heat generated by the acoustic wave radiator, and efficiently transferring said heat to the surroundings. The corrosion-resistant heat-sink chamber 460 is pressurized to prevent cavitation phenomena that may be generated through the application of sound waves. The value of internal pressure in the corrosion-resistant heat-sink chamber is adjusted depending on individual characteristics of formation and of the power level used.
The controlled environment chamber 464 may be fabricated of a material resistant to mechanical waves generated by the wave radiators 430. Inside the controlled environment chamber are measurement and control sensors 435. The main objective of this controlled environment chamber is to protect said sensors from corrosion and degradation due to hydrocarbons present in the formation, and from the waves produced by the one or more wave radiators 430.
Chamber 460 may be compartmentalized into two or more sub-chambers (e.g., 462 and 464) and the sub-chambers may be interconnected to allow free passage of the heat-sink liquid.
The purpose of measurement and control sensors 435 is to acquire information about temperature in the internal space of the chambers, reservoir pressure, and structural integrity of the chamber wall 440. This information is used to affect an automatic and/or manual control of the acoustic device 400, to optimize hydrocarbon extraction from the formation, or to detect operation failures of the device.
In embodiments of the invention, magnetostrictive transducers may be used. Such transducers need to be coiled by a special kind of wire: The wire must resist high electric currents (which in some cases may rise over 200 Amperes), and high temperatures (over 200° C.) and corrosion. Teflon insulated wires could be used to surpass the corrosion and high temperature issues. To resist high electric currents the cable's gauge should be determined to fit the specific requirements of the application (e.g. to resist currents up to 41 Amperes, a AWG #12 cable is advised).
In other embodiments, where the magnetostrictive transducers are protected from corrosion and from high temperatures, the cable's insulation could be modified in order to diminish the volume occupied by the coil, e.g., enameled wire could be used instead of Teflon.
Block 510 represents a control unit, that provide a user and/or system to select the power level and regime (e.g., operating frequencies) to drive the magnetostrictive devices. Block 520 represents a power supply unit that receives power 530 input (e.g., from a tri-phasic power line having three lines of 380 Volts). Block 540 represents a component for generating power for an ultrasonic power generator. Its output (e.g., 550) may for example be a 520 Volts at 23,000 KHz. Block 560 represent the power generator for a magnetizing current. The output current (e.g. 570) may be for example a 10 Amperes current.
The power generator, as represented in
Attachment Cables and Power Supply Lines
Magnetostrictive Device Manufacturing Process
Acoustic waves may be generated by means of a transducer (e.g., 310). This transducer may utilize a piezoelectric or magnetostrictive, or any other means capable of generating elastic waves. In one embodiment of the invention, the device 400 utilizes a magnetostrictive transducer. It is preferred that the material of the transducer was not only magnetostrictive, but also soft magnetic. A magnetostrictive material is one that undergoes physical change in shape and size when subjected to a magnetic field. On the other hand, soft magnetic materials become magnetic in the presence of an electric field, but retain little or no magnetism after the field is removed. Many well known alloys have these characteristics, being suitable for this application, for example nickel-iron or cobalt-iron alloys. An iron-cobalt-vanadium alloy was used in embodiments of the invention, such alloys are available for example under the commercial names of Permendur and Supermendur. The invention may be practiced, however, with any alloys that presents the characteristics described above.
To avoid losses due to eddy currents, it is preferred to form each transducer with a stack of plates of the magnetostrictive material with a layer of a dielectric material in between each plate. The plates need to be thin enough to avoid eddy currents but sufficiently thick to have a magnetostrictive effect that would successfully produce the required acoustic waves. According to the invention, plates may have a thickness of between 0.1 mm and 4 mm. In one embodiment of the invention, the plates have a thickness of 0.15 mm thickness.
The magnetostrictive principle works with a plurality of geometries. The device, according to one embodiment of the invention, utilizes the length of the plates as determined to be half of the wavelength of the mechanical waves in said magnetostrictive material. The latter maximizes the elastic wave generation.
At step 730, a resin is applied to the plates. Then, at step 740, the plates are stacked. Each transducer may have, for example, between 100 and 400 plates, and in one embodiment of the invention a transducer may utilize between 250 and 350 plates. To avoid losses due to undesired longitudinal waves, the transducer height (given by the number of plates) and width should be similar. The dielectric material can be for example an epoxy resin. In this case, the resin under the trade name Sintepox LE 828 was used. The thickness of the dielectric layer can be between 0.01 mm and 0.05 mm, and a 0.025 mm thickness was used in the present device. The application of the resin can be done in several ways. For example, the resin may be manually applied using a brush, soaking the plates in the resin, with an aerosol or with any other available means for applying resin.
The stacking of the plates can be done manually or automatically. After applying the resin the plates are stacked applying pressure to eliminate resin excess and control the dielectric layer thickness. At step 750, the plates are dried using an optimal curing temperature according to the resin data sheet.
During operation, a wave generator in accordance to the invention produces mechanical vibrations. The mechanical vibrations promote formation of shearing vibration in an extraction zone, due to phase displacement of mechanical vibrations produced along one axis of the well, thus achieving alternating tension and pressure forces due to superposition of longitudinal shear waves, and so stimulating the mass transfer processes within the well.
Elastic Waves Propagation
Radial vibrations through the radiant surface (32) of either the elastic wave radiator (32) or the chamber are transmitted to the inside of the reservoir (33) surrounding the well. Velocity vector VZ1 (34) of longitudinal vibrations is propagated to the reservoir (33) surrounding the well in a direction perpendicular to the longitudinal axis of the chamber. Diagram 35 shows the radial distribution characteristic of displacement amplitudes ξZml(39) of radial vibrations propagated to the reservoir (33) surrounding the well; they are radiated from points of the chamber that may be located at a distance equal to λ/2, λ being the wavelength of longitudinal waves in the material of resonance chamber.
Phase displacement of radial vibrations propagating in the medium generates shearing vibrations in a perforated region of the well, whose oscillating velocity vector VZS (36) is directed along the axis of the chamber. Diagram 37 shows the characteristic distribution of displacement amplitudes of shearing vibrations ξZmS.
As a result of the superposition of longitudinal and shearing waves, an acoustic flow (jet streaming 38) is produced in the perforated region of the well (e.g., 210), improving the desired effect of viscosity reduction and mass transfer.
Layout Example of a Plurality of Elastic Wave Generators within a Device
For example, a radiant surface 902 having a tubular geometric shape, with an external diameter DO, and geometric dimensions of radiant surface, length “L” and wall thickness “λ” may be determined by working conditions under resonance parameters of radial and longitudinal vibrations, at natural resonance frequency of the wave radiator. To implement the principle above indicated, regarding formation of a superposition of longitudinal- and shear waves in the perforated region of the well, the length “L” of the chamber should be at least half of the longitudinal wavelength λ of the acoustic wave inside the material of the radiant surface; that is, L≧λ/2, e.g., in an oil well with a chamber made of stainless steel, the sound velocity in such stainless steel at 100 atm pressure is approximately 6000 m/s, and the radiator operating at a 25 KHz frequency, the wavelength is 24 cm, thus the length ‘L’ must be at least 12 cm long.
Resonance Chamber and Guidelines for Construction and Layout of Elastic Waves Generators
Alternative Layouts for Vibration Transmission
An acoustic wave generator, such as 1140, may be mounted so as not directly touch the wall 1145. The acoustic wave energy is then transmitted to the wall 1145 through the liquid 1141. In an other instance, an acoustic wave generator, such as 1150 may be connected to the wall 1155 through a wave guide 1158. The wave energy, in the latter case, is transmitted to the wall 1155 through both the liquid 1151 and the wave guide 1158.
Several dispositions of one or more wave radiators may be implemented. For example:
In the embodiment shown in
Alternative Mounting Layout of Device in the Well
Methods for Applying Elastic Waves Stimulation
Following the pre-installation, one or more treatments may be carried depending on the type of well, the resource to be extracted and the state of the resource to be extracted. For example, depending on the content in gas of an oil well, or the viscosity of the crude oil in the well, a determination may be made to treat the well in one or many ways before the system is permanently installed and operated.
For example steps 1520, 1530 and 1540, respectively represent stages of well cleaning, heat treatment of the well and/or cleaning a well under pressure. Once the well has undergone one or more treatments (e.g., steps 1520, 1530 and 1540), the tool can be permanently installed and operated in-situ.
At step 1610, the device geophysical cable is connected. Connection is made between the acoustic tool and the geophysical cable. Step 1610 involves connecting the positioned tool in the wellbottom, wellbore or perforated zone of the well, to a geophysical cable of a proper length. In addition, step 1610 involves checking the electrical connections through continuity tests.
At step 1615, the device implementing the invention is joined to the tubing. The latter step involves connecting the device to the tubing, using for example, a standard couple in the oil industry.
At step 1620, a device implementing the invention is deployed. The latter step involves installing a tuning string with the acoustic tool attached to its end through a rig truck and a temporal wellhead. The latter step also comprises checking the electrical connections through continuity test.
At step 1730, pressure and temperature are surveyed, among other physical variables (e.g. viscosity). The latter step involves measuring temperature and pressure profiles before the acoustic well stimulation. Further temperature and pressure measurements are conducted after the acoustic stimulation, and the profiles are compared in order to determine the changes that are the result of the acoustic treatment.
At step 1735, a device implementing the invention is temporarily positioned at a point of interest (e.g., wellbottom, wellbore or perforated zone of the well) in order to conduct well cleaning at that particular point of interest.
At step 1740, the device is started, which involves switching on the ultrasonic generator, setting up the working parameters (frequency, current and power). The latter step further involves checking the correct functioning of the system through current and voltage measurements at the output of the generator.
At step 1745, the point of interest previously selected is cleaned by temporarily operating the acoustic device in a specific depth, and its subsequent repositioning to another point of interest.
At step 1750, a measurement of fluid level is carried out of the liquid in the wellbottom, wellbore and/or the perforated, by means of adequate tools (e.g. EchoMeter). The latter measurement may be crucial in order to maintain the pressure in the wellbottom so that an efficient acoustic power transmission is achieved.
At step 1860, the point of interest where the device was positioned is cleaned by temporary action of the acoustic tool at a specific depth, and its subsequent repositioning to another point of interest.
At step 1870, the pressure is released following the cleaning at every depth in order to stimulate the movement of the obstructive particles and their natural decantation to the wellbottom.
At step 1905, a well is flooded (similarly as described above). At step 1910, the heating device is installed along the tubing (as described in
At step 1970, the well is cleaned as described above. At step 1980, the level of fluid is measured for further adjustment of the treatment time and parameters.
At step 2020, well landing is carried out. The latter step involves installing and deploying a pumping device. This stage includes the removal of the temporal wellhead of the well, the disconnection of the geophysical cable from the generator, the connection of the geophysical cable to the permanent wellhead of the well. The well is closed and sealed
At step 2030, the permanent regime is started. The latter step involves acoustically stimulating the well in a permanent regime, which may be carried out concomitantly with oil extraction.
At step 2040, the well and the device are monitored, and one or more operating parameters of the acoustic stimulation system (frequency, power and magnetizing current) may be modified to optimize the performance of the treatment.
Low-Frequency Application Through Modulation of High-Frequency Elastic Waves
During operation, a device for generating acoustic waves in accordance with embodiments of the invention may be operated using a continuous power signal, a pulsed signal or any other mode a user may determined appropriate for any given treatment. For example, control system 110, may deliver power to the wave generator in wide range of power and frequency, where the level may be determined by the user and/or a control system 110.
In embodiments of the invention, the data processing and control system (e.g., 110) may be utilized to drive the wave radiator, by providing for example, instructions to the wave radiator, which instructions will be used by the wave radiator to vary the power output to the geological formation in order to achieve the best results. The data processing and control unit may on the other hand control the power directly fed into the wave radiator in order to control the amount of power delivered to the reservoir.
In embodiments of the invention, the wave radiator may be deliver acoustic waves, mechanical waves, electromagnetic waves or any type of physical phenomenon capable of delivering vibrational energy to a geological formation.
A control system implementing the invention enables the system to irradiate the geological formation in any operating regime the user desires, including continued, alternated, pulsed, in amplitude modulation, frequency modulation, among many other possibilities.
The soil is expected to behave as a natural low-pass filter. At a certain distance, the soil filters the signal, attenuating the high frequency components, thus acting as a demodulator of an amplitude modulated (AM) signal.
Because of the integration properties of a low pass-filters in general, and of the soil with regard to acoustic waves in the present case, a burst of high-frequency waves results in a low frequency power transfer wave.
Low-frequency acoustic waves are able to travel longer distances. The generation of low-frequency signals provided by a system embodying the invention by modulating high-frequency signals allows for a wide range of application of low-frequency stimulation along with high-frequency stimulation.
The soil's properties to dampen acoustic vibrations amplitude as the vibration frequency increases may modeled as a low-pass filter having a bandwidth of
Bw=[0, fc]
Where “fc” is the soil's cutoff frequency, that may vary depending on the type of soil being treated.
This low-pass filter can be modeled as follows:
where
and where “H(s)” is the low pass filter transfer function; “K” is the gain of the filter, “s” is the frequency domain variable; “ξ” is a damping ratio of the system; and “fc” is cutoff frequency of the low-pass filter.
A system embodying the invention is enabled, to exploit the inherent low-pass filter properties of the soil, coupled with the ability of embodiments of the invention to generate and modulate high-frequency signals in order to apply low-frequency acoustic waves to the geological formation.
In a system embodying the invention, amplitude modulation can be achieved when the control system regulates the output power of the ultrasonic generator. If the generator gradually periodically decreases and increases the output power repeatedly the amplitude can thus be modulated.
Frequency modulation of signals allows for irradiating in a wide bandwidth; where the user via the control system sets the stimulation bandwidth. This is very useful when information about the treated well is unavailable. This stimulation bandwidth could be for example between 15 kHz to 25 kHz, in this case the control system would gradually increase the ultrasonic generator's frequency from 15 kHz to 25 kHz and then gradually decrease it to 15 kHz, this process may be repeated while the frequency modulation operating regime is enabled.
Pulsed and AM modulated operation, as they radiate high frequency and also low frequency acoustic waves, they are useful to increase the mobility of oils deep into the reservoir, because low frequency acoustic waves travel further than high frequency.
General Method of Combining EOR Treatment with Application of Elastic Waves
As briefly described above, the invention provides a method, apparatus and system for a combined application of elastic waves and one or more available technologies for stimulating production in a well. In the case of oil/gas recovery, the latter techniques are commonly referred as enhanced oil recovery (EOR) treatments.
At step 2430, deployment of the machinery of the selected EOR is undertaken. In the industry of oil production, the latter step may require calling for a team of workers whose expertise is the assessment of the well, the selection of the necessary logistics to carry out the EOR treatment, the deployment of the machinery, the application of the treatment, and the cleanup stage at the end of the treatment.
Following the installation of the EOR machinery, the EOR treatment may be started at step 2440. Starting an EOR treatment involves specific steps that are selected for the type of EOR treatment. Owing to the data collecting system of an embodiment of the invention physical parameters such as temperature, pressure, acidity and the like, are provided as input to the EOR technique which may contribute to adjusting some treatment parameters even before the start of the EOR treatment.
At step 2450, the treatment with the elastic waves may be started. Step 2450 may be undertaken before, during or following step 2440. Owing to the remote control provided by an implementation of the invention, treatment with elastic waves may be optimally adjusted to maximize the synergistic effect of the vibrational treatment and the EOR treatment. For example, when acidizing a well, the operator of the EOR treatment may find it useful to stop the elastic wave treatment during specific stages of the acidizing treatment.
At step 2460, data is collected periodically or in real-time and analyzed in order to assess the progress of the well stimulation. Based on the ongoing assessment, a treatment may be continued at step 2440. Otherwise, if the goal of the treatment has been achieved, the treatment is stopped, the treatment machinery retrieved and the follow up procedure to clean up the treatment spent fluids may ensue.
One with ordinary skills in the art of EOR treatments is typically familiar with each type of treatment. Although, these treatments share some general steps in the methods of deployment and execution, in practice the level of skills acquired with each EOR technology increases with the amount of experience a person or a team thereof accumulate during their practice. It is common that a different team of experts is called upon for a given treatment. Therefore, the invention
Hydraulic Fracturing Combined with Elastic Waves Application
The invention provides a combination of applying hydraulic fracturing with elastic waves treatment. Hydraulic fracturing relies on the high pressure exerted on the rock formation (or shale) in order to crack open fissures in the rock or widen the existing ones. Furthermore, the water used to exert the high pressure is loaded with solid particles (e.g., sand grains, gravel, pebbles and the like) that are wedged inside the fissures, and remain permanently lodged in the fissures in order to keep the fissures open after the pressure has been removed.
The pressure waves created by the application of elastic waves, in accordance with the teachings on the invention, may travel to varying distances from the well, depending on the frequency and power of the elastic waves. The effects of applying elastic waves to a well in combination with fracturing treatments, in accordance with embodiments of the invention, lead to a long-lasting treatment effect, an increase of oil mobility through new fractures, increased mobility of proppant particles through cracks in order to keep openings wider and, hence, lasting long for fluid flow.
At step 2520, the machinery for applying hydraulic treatment is deployed. The latter involves setting up a water supply source, lowering the tubes into the well, installing plugs to isolate a given portion of the well to be treated with high pressure. At step 2530, water is pumped into the well and the pressure is raised to levels sufficient to cause fissures to open inside the rock formation (or shale).
At step 2540, proppant (e.g., sand and/or any other solid particles used to lodge inside the fissures) is added to the water. The latter mixture is blended at step 2550. Then at step 2560, the mixture is pumped into the downhole.
Following the treatment with the combination of hydraulic fracturing and elastic waves application, the treatment's spent fluids are recovered and the well is cleaned in preparation for production.
Gas Injection Combined with Elastic Waves Application
Within a reservoir, of oil/gas for example, the natural resource may travel over time from one area to another area of the reservoir, and/or diminish in all areas or in some areas faster than others. The latter is due to several factors, among which that extraction of the resource from the reservoir reduces the overall pressure to a point where some wells become insufficiently productive. In other instances the movement of fluids such oil and/or underground water causes the natural resource to shift. Movement of fluids as well as seismic type movement, land slide and the like may be responsible for such natural resource movement.
Enhanced Oil Recovery treatment tackle this issue by selecting some wells (e.g., depleted or non-producing wells) to inject a fluid under pressure that results in exerting pressure within the reservoir to push the natural resource toward the other producing wells in a production field. The injected fluid may be water and/or gas.
In a typical oil field, the fluids pumped out of wells typically contain, in addition to crude oil and natural gas, water and other gases such as carbon dioxide (CO2) and hydrogen sulfide (H2S). Crude oil and natural gas are separated from the mixture and recovered. But, the residual water and the gasses typically present a burden to dispose of them. These fluids can be re-injected inside the reservoir for permanent disposal.
When injection of water and/or residual gases is properly planned, an EOR treatment-based injection of fluids can be designed to raise the pressure in a reservoir. To the latter end, a study is conducted to determine the state of the reservoir. Then some wells (e.g., depleted wells) are chosen for injection of fluids.
The invention teaches a combination of applying fluid injection in some wells with the treatment with elastic waves using an apparatus embodying the invention which is deployed in one or more injection wells and/or neighboring producing wells. The effect of a treatment in accordance with embodiments of the invention, is a synergistic effect whereby the movement of the injected fluid is facilitated by the pressure waves produced by the apparatus.
At step 2620, the gasses and water from at least one well are collected and separated from the fluids pumped out of at least one well. Typically, the fluids are collected form a plurality of wells.
At step 2630, the gases recovered from the reservoir are treated with amine-bases chemicals. The result of the latter processing is a separation of CO2 and H2S from the recovered fluids. The latter processing method is well known in the art of oil and/or gas recovery and refinery.
At step 2640, the recovered gases are compressed under high pressure (e.g., using a compressor) and stored in high-pressure tanks. Simultaneously, water is also recovered at step 2650, and water vapor is recovered at step 2660.
At step 2670, the water, water vapor and recovered (then treated) gases are mixed. Then at step 2680, the mixture is injected under high-pressure. In accordance with the teaching of the invention, while the mixture is being injected into the well, and/or following the injection of the mixture, elastic pressure waves may be applied from a device embodying the invention. The result of the pressure waves application is a faster diffusion of the fluids through the rock formation or shale. Thus, the application of the elastic wave facilitates the build up of pressure in the rock formation (or shale) with a pressure gradient that is highest at the injection well, thus, decompression results in pushing the fluids toward the producing wells.
The benefit of the combination of treatment of wells with elastic waves along with fluid injection treatment include a faster result, which reduces the time (and cost) of treatment, and increasing the capacity of the reservoir to absorb more of the waste gases and water. Furthermore, owing to the physical characteristics of elastic waves
Acidizing Combined with Elastic Waves Application
The inventions provides a combination of using existing acidizing methods of a well with the application of elastic waves to the well bore and the rock formation (or shale). When a rock formation (e.g., limestone or dolomite) contains compounds that are soluble in water, small amounts of the soluble compounds tend to be deposited, which over time tends to narrow the pores and/fissures, and ultimately obstruct openings in the well casing, and passage ways through the fissures in the rock formation. The application of an acidic water solution, in a process called acidizing, may be carried out to reopen previous passage ways, or etch new ones. The latter process consists of running a highly acidic solution in the well in order to dissolve mineral deposits (e.g., carbonate deposits) and sediments. Pumping the acid into the rock forces the creation of channels that connect the formation with the well bore, thus, creating passage ways for oil and gas to flow into the well bore and be collected.
Acidizing creates a very caustic environment, hence, careful planning is required to be able to attack the target minerals and etch the rock while protecting the treatment equipment and the well structure.
At step 2740, an apparatus for generating elastic waves embodying the invention is deployed in an area selected for treatment. Step 2740 may be carried out at any stage of the treatment. For example, an apparatus for generating elastic waves may be deployed after the acid has been pumped into the well.
At step 2750, the acid solution is injected into the well at a high pressure. At step 2760, elastic-wave stimulation may be carried out during the application of the acid solution. As described above, pressure waves having various frequencies provide a synergistic effect on the action of the acidizing process at several levels, comprising improving the mixing of the acidic solution with the substrates and facilitating the flow of the solution deeper into the fissures in the rock. The benefit of such synergistic effect is a deeper penetration of the acid into the surface of rock and a farther travel of the acid into the formation. The latter benefits may shorten the time of the treatment, thus, reducing treatment costs, increase the production rate of the well, and prolong the time the well is productive before it needs a treatment again.
Thus an apparatus, method and system for increasing production of a natural resource producing-well, by utilizing an acoustic waves generating device to deliver vibrational energy to the geological formation and continuously monitoring and optimizing the stimulation parameters. Furthermore, by combining the acoustic treatment with existing EOR treatments, the invention provides a method apparatus and system for improving the results of any available EOR treatment.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12954906 | Nov 2010 | US |
| Child | 13029108 | US |
